System and method for accurately weighing and characterizing moving vehicles

• US 5,959,259 A
• Filed: 03/11/1997
• Issued: 09/28/1999
• Est. Priority Date: 03/11/1997
• Status: Expired due to Term

• Current Assignee: Lockheed Martin Energy Research Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Energy Research Corporation (Martin Marietta Corporation)
• Inventors: Capps, Gary J., LaForge, John V., White, Cliff P., Beshears, David L., Muhs, Jeffrey D., Jordan, John K., Scudiere, Matthew B., Nodine, Robert N.
• Primary Examiner(s): Gibson, Randy W.
• Application Number:
  US08/815,107
• Time in Patent Office: 931 Days
• Field of Search: 177/132, 177/133, 177/136, 177/25.13, 177/134
• US Class Current: 177/132
• CPC Class Codes: G01G 19/022 for weighing wheeled or rolling bodies in motion G01G19/045 takes precedence
• CPC Class Codes: G08G 1/015 with provision for distinguishing between two or more types of vehicles, e.g. between motor-cars and cycles

Abstract

This system and method of operation weighs and characterizes a moving vehicle traveling on a roadway. The moving vehicle travels across a weight transducer and first and second switching devices. The transducer provides a first set of output signals indicative of vehicle tire loading. The switching devices provide second output signals indicative of vehicle speed and characterization. Processor means receive the first and second output signals and characterize the vehicle; calculate the vehicle speed and calculate the vehicle weight by integrating the second output signals and combining with the vehicle speed.

Claims

1. A system for weighing moving vehicles comprising:

a) a weight transducer extending in the direction of vehicle travel and positioned in the path of a moving vehicle;

the transducer providing first output signals indicative of the vehicle loading in the direction of vehicle travel as the vehicle travels across the transducer;

b) a vehicle speed sensor providing second output signals indicative of the vehicle speed as the vehicle travels across the transducer;

c) a processor for receiving the first and second output signals; and

d) programmable instructions stored in the processor for controlling the processor to calculate the weight of the moving vehicle by integrating substantially all of the first output signal over time as the vehicle travels over the transducer and multiplying the integration result by the vehicle speed and a calibration constant that is substantially invariant for differing types of vehicle tire footprints, weights, and speeds.

3. The system of claim 1 wherein the processor means conclude a data acquisition processor and a control processor and the first output signals comprise Tx*Wx where Tx is the vehicle tire loading on the weight transducer in the direction of travel;

Wx is the weight transducer response in the direction of travel and * is a symbol for a convolution integration.

4. The system of claim 3 further comprising means for coupling together the data acquisition processor and the control processor and wherein the convolution integration is a linear transform of an integral of Tx multiplied by an integral of Wx.

5. The system of claim 3 wherein the vehicle speed sensor comprises duplicate paired switches providing multiple sets of signals for redundancy in determining vehicle speed independent of tire configuration and the transducer comprises a first element and a second spaced element, each element coupled to a separate data acquisition processor.

6. The system of claim 3 further comprising means for coupling the first and second output signals to the data acquisition processor.

7. The system of claim 6 further including weight monitoring and switch monitoring circuits coupled to the data acquisition processor.

8. The system of claim 7 further including a sample clock circuit and counters coupled to the data acquisition processor.

9. The system of claim 8 further including an axle timer, a transducer timer and a watch dog timer coupled to the data acquisition processor.

10. The system of claim 9 further including a FIFO buffer coupled to the data acquisition processor and the control processor.

11. The system of claim 10 further including a status register coupled to the data acquisition processor and the control processor.

12. The system of claim 11 including a first memory coupled to the data acquisition processor and a second memory coupled to the control processor.

13. The system of claim 12 further including stored program instructions in the first memory for starting the timers;

time stamping and storing switching events as the vehicle traverses the switching means.

14. The system of claim 13 further including stored program instruction for starting the timers;

time stamping weight values generated by the transducers and storing the weight values as the vehicle traverses the transducer.

2. A method for weighing in a system including a weight transducer extending in the direction of vehicle travel and positioned in the path of a moving vehicle, a vehicle speed sensor for detecting the speed of a vehicle as it travels over the weight transducer, and a processor including stored program instructions, said method for weighing the vehicle as it travels over the weight transducer, comprising the steps of:

a) providing first output signals indicative of the vehicle loading in the direction of vehicle travel as the vehicle travels across the transducer;

b) providing second output signals indicative of the vehicle speed as the vehicle travels across the transducer;

c) calculating the speed of the vehicle as it travels across the transducer; and

d) calculating the weight of the vehicle by integrating substantially all of the first output signal over time as the vehicle travels over the transducer and multiplying the integration result by the vehicle speed and a calibration constant that is substantially invariant for different types of vehicle tire footprints, weights, and speeds.

15. The method of claim 2 further comprising the step of storing the first and second output signals as data in a memory and wherein the first output signals comprise Tx*Wx where Tx is the vehicle tire loading on the weight transducer in the direction of travel;

Wx is the weight transducer response in the direction of travel and * is a symbol for a convolution integration.

16. The method of claim 15 further comprising the step of sorting the data to determine the end of a tire traversing the switching means and wherein the convolution integration is a linear transform of the integral of Tx multiplied by the integral of Wx over the entire weight transducer.

17. The method of claim 15 further comprising the step of performing a consistency check on the stored data.

18. The method of claim 15, wherein the vehicle speed sensor comprises a first pair of switches located before the transducer in the direction of vehicle travel and a second pair of switch located after the transducer in the direction of vehicle travel, further comprising the step of calculating the vehicle speed from the actuation of the first and second pairs of switches as the vehicle traverses the switches.

19. The method of claim 18 further comprising the step of calculating the vehicle wheel spacing as the vehicle traverses the switches.

20. The method of claim 19 further comprising the step of calculating the vehicle tire lengths as the vehicle traverses the switches.

21. The method of claim 15 wherein the transducer generates the waveform Tx*Wx as the vehicle traverses the transducer.

22. The method of claim 2 further comprising the step of displaying the weight on a display device.

23. An article of manufacturing, comprising:

a computer usable medium having computer readable program code embodied therein for weighing moving vehicles, the computer readable program code in said article of manufacturing, comprising performing the steps of;

a) receiving first output signals indicative of vehicle loading in a direction of vehicle travel as the vehicle travels across a transducer;

b) receiving second output signals indicative of vehicle speed as the vehicle travels across the transducer;

c) calculating the speed of the vehicle as the vehicle travels across the transducer using the second output signals; and

d) calculating weight of the vehicle by integrating substantially all of the first output signal over time as the vehicle travels over the transducer and multiplying the integration result by the vehicle speed and a calibration constant that is substantially invariant for differing types of vehicle tire footprints, weights, and speeds.

24. A system for weighing and characterizing moving vehicles comprising:

a) a weight transducer having an entrance and an exit and positioned in the path of a moving vehicle;

the transducer providing first output signals indicative of the vehicle loading as the vehicle travels across the transducer;

b) duplicate paired switches positioned before the entrance and after the exit of the transducer;

whereby the switches provide multiple sets of second output signals indicative of the vehicle speed, number and spacing of vehicle axles, regardless of vehicle tire footprint as the vehicles travels across the switches;

c) a data acquisition unit coupled to the weight transducer and the switches for collecting and storing the first and second output signals;

the data acquisition unit including a sample clock circuit and counters;

an axle timer, a transducer timer, and a watchdog timer;

a FIFO buffer and stored program instructions in a first memory for starting the timers;

time stamping and storing switching events as the vehicle traverses the switches;

d) a processor for controlling the data acquisition unit and receiving the first and second stored output signals; and

e) programmable instructions stored in the processor for starting and stopping and transferring data from the data acquisition unit and controlling the processor to calculate the weight of the moving vehicle by integrating substantially all of the first output signal over time as the vehicle travels over the transducer and multiplying the integration result by the vehicle speed and a calibration constant that is substantially invariant for differing types of vehicle tire footprints, weights, and speeds.

25. In a system including a weight transducer having an entrance and an exit and positioned in the path of a moving vehicle, a first pair of switches positioned before the entrance and a second pair of switches positioned after the exit of the transducer, a data acquisition unit, and a processor including stored program instructions, a method for weighing moving vehicles, comprising the steps of:

a) providing first output signals indicative of the vehicle loading as the vehicle travels across the transducer;

b) providing multiple sets of second output signals as data indicative of the vehicle speed as the vehicle travels across the switching means;

c) starting an axle timer and a pad timer for vehicle velocity and axle spacing calculations;

d) starting a wheel watchdog timer for vehicle weight calculations;

e) sorting the data to determine the end of a tire traversing the switching means;

f) stopping the axle, pad, and watchdog timers after collection of the data;

g) performing a consistency check on the stored data;

h) calculating the speed of the vehicle using the multiple sets of second output signals; and

i) calculating the weight of the vehicle by integrating substantially all of the first output signal over time as the vehicle travels over the transducer and multiplying the integration result by the vehicle speed and a calibration constant that is substantially invariant for differing types of vehicle tire footprints, weights, and speeds.